Method of making oil hole twist drills



. Sept. 19, 1944. s. A. COGSDILL ,3 3

METHOD OF MAKING OIL HOLE TWIST DRILL Filed' Dec. '7, 1942 INVENTOR A TTORNEY$ Patented Sept. 19, 1944 METHOD OF MAKING on. HOLE 'rwls'r DRILLS Stuart A. Cogsdill, Detroit, Mich,- assignor to v Cogsdill Twist Drill 00., Detroit, Mich., a corporation of Michigan Application December '7, 1942, Serial No. 468,061 6 Claims, (or 76-408) This invention relates to twist drills and particularly to twist drills having a liquid passage extending from the shank end thereof to the I point end thereof for the purpose of introducing a flow of coolant or lubricating liquid to the cutting edge of the drill during a drilling operation, the principal object being the provision of an improved method of making such drills in an eflicient and economical manner.

Objects of the invention include the provision of a method of making oil hole twist drills including the step of forming a longitudinally extending groove in a surface of a blank therefor and lips or ridges along each side of such groove, then working said lips or ridges toward and into sealing engagement with each other whereby to close the open side of said groove and thereby form a hole in said blank; the provision of a companying drawing, and then claimed, having the above and other objects in view.

Inthe accompanying drawing which illustrates suitable steps of operation in the manufacture of an oil hole twist drill in accordance with the preferred practice of the present invention, together with a drill constructed in accordance with the present invention, and in which like numerals refer to like parts throughout the several difler.

en-tviews, r

i Fig. 1 is a side elevational View of a drill blank in partially completed condition;

Fig. 2 is an enlarged transverse, sectional View taken onthe line 2--2 of Fig. 1, and illustrating method as above described in which the surface working said lips or beads together to close the first-mentioned groove; and the provision Of a method of making oil hole drills as above described in which the depth of the second groove is substantially equal to the amount of clearance desired back of each trailing edge of the associated flute of the drill.

Further objects of the invention include the provision of a method of making oil hole twist drills comprising forming a straight and longituthe type of tool preferably employed for forming the grooves in the blank, which grooves are later to be converted into oil holes;

Fig. 3 is a fragmentary, sectional View taken diametrically throughthe upper end of the drill blank shown in Fig. 1 to illustrate the bore therein and the passages connecting it to the grooves which are later formed into the oil holes;

' Fig. 4 is a view similar to Fig. 2 but illustrating a machining operation upon the blank to form lips or beads alongeach side of the groove and which operation, as hereinafter brought out, may if desired be accomplished simultaneously with the operation disclosed in Fig. 2;

Fig. 5 is a view similar to Figs. 2 and 4, but illustrating the operation of closing the outer side of the grooves to form the oil holes; v

Fig. 6 is a transverse, sectional view through the drill blank illustrating a step of operation dinally extending groove in the surface of a cylindrical drill blank, closing the Open side of the groove by working the metal of the blank on either side thereof into contacting relationship along the center of the groove, and thereafter twisting the blank into spiral conformation; the I provision of a method of making an oil hole twist drill as above described in which the groove is closed before the flutes are'machined in the blank and the flutes are machined in parallel relation to the grooves in the blank; and the provision of a method of making an oil hole twist drill in thereon following the closing of the grooves therein; I a Fig. 7 is a View similar to Fig. 6 but illustrating the operation on the drill blank following that shownin Fig. 6; and, Fig. 8 is a side elevational view of the completed drill.

In myprior United States Letters Patent No. 2,148,805, issued February 28, 1939-, on Method of making oil hole drills, a method of making suchdrills is disclosed in which grooves are machined in the lands of the drill at the same spiral as the flutes thereof and thereafter the metal of the lands on each side of each of such grooves is worked inwardly to close the open side of such grooves, thereby to form so-called oil holes or passages through which lubricant, suitable coolant or other fluid, may be fed to the point of, the drill for well-known reasons- Since the issuance of said patent, experience has shown that particularly with the high speed steels employed in modern drill manufacture, the

mation-of theflutes. The rea-son for soformstand.distortioniunderrthe force of the closing method there disclosed for closing the open sides of the grooves while possible, was commercially inadequate in that the working of the metal over the open side of the groove was too difiicult and too often resulted in. an imperfect closure of the 5 open side of the groove. In accordance with one phase of the present invention, I have discovered that the closure-of the-open side of such groove may begreatlyfacilitated and the occasional imperfect closure of the groove in the former case be eliminated if an upstanding bead or lip is formed at each side of the groove at-the open side thereof and is then operated upon to work it inwardly toward the center of the groove, as by an operation something akin to -a"-*- -sired" spiral conformation, for the purpose of illustration the preferred method is illustrated bending operation instead of a true-'metalflowing operation as in the case of my prior patent, until the beads or lips at opposite sides of each groove are brought into contacting and sealing relation with respect to each other. The formation of these lips-onbeadsat-opposite sides-of each groove provide a. construction in which-lthe metal" constituting the samemay -be-readily'*displaced inwardly to 1 close the: open side of the groove in a much easier and "efficient'im'anner J than that suggested'tinmy'prior patent and .with

' materially lessforcerequiredinithefclosingroperv fation.

In: the: broaderi'aspects TOf thepresnt' invention, the formation of these lips or beads'nalong eachside of the groovewhich1is toform-' an oil closed; and thereafter the blank twisted -to*-the desired spiral conformation. V 7 Furthermore, while such grooves ""may be' formed in the" blanks after the flutes havebeen formed therein, the "grooves' are preferably formed in the blank and closed prior'to the foring the grooves and closing-them as -least-described is because-in-actuarpractice-in the-formation of oil holedrillsasdisclosed in my prior patent above identified," it was "found that the closing operation, that is; the displacing ofmetal inwardly from the open. sides of thetgro'oves closed suchiopen= sides, "wasfextremely difficult when the "grooves" were already of :spiral conformation, for the reason "that'thefblankihad a tendency to slip sideways, or "axially' of. .the {'60 rolls employed inthe closing. operation, and that when such slippage A occurred an" unequal; .displacement of the metal on opposite sides of. the grooves occurred and often resulted in anl .imperfect closure of the 'opens'ide'Jof itheigroove. In accordance withflthis further .fph'ase 'offithe presentinvention, IJhave'discovered that if the grooves are straight and particularly 'if.they are closed prior tothe formation of'the flutes in the"drill,blanks,ithe drillblank maybe more ac- .79 curatelyand easily guided. between; the rolls employed for workingjthe metal over the open sides thereof, the blank is btteri-able to withrb11s,. aad suchlclosure .may be: accomplished in a quicker, more economical and more efficient manner, resulting in a more perfect product.

Although, as above described, the provision of the lips or beads along each side of the grooves which are to form the oil holes in the finished product is applicable to the manufacture of such oil hole drills whether such grooves are formed in the drillblank atth'e spiral required in the finishedproduct, or are formed straight and thereafter the blank is twisted to the desired spiral conformation, and although the flutes in -the drill'may be initially formed of the desired e-s'piral conformation desired in the finished product, or may be formed straight and the blank thereafter twisted to bring the flutes to the de- Iin the accompanying drawing as being that in which both the grooves and the flutes are formed straight in the blank and the blank thereafter twisted to bringthefiutes to their-desired spiral conformation. Also, althoughthe grooves may be closed either beforeor afterthefiutes are formedin thedrill blank-,- as a matter of illustration "the: steps -of operation illustrated in the accompanying drawing-are those in Which'the grooveis closed prior-to the formation of the fiues as=this is the preferred practice in accordance with the present-invention.

Additionally, although the grooves and the'lips bounding the opposite sides of the same maybe formed simultaneously -in asingle machining operation, for the purpose of clarity in description-in-the accompanying drawing the groove and 5 the lips are shown as being formed by'independentma'chining operations. Itwill, therefore,'be understood that the showing in the drawing and the following explanation of the same is that of the preferred method of making oil hole twist fld-rills in aocordance' with the present invention,

butthat'the variations inmanufacturing procedure above'outlined are withinthe scope of the present invention'and are'covered herein where the language of the claims permits.

Referring now to theaccompanying drawing, and particularly to Fig. 1, the'drill blankthere shown comprises a-m'ainbody portion 10 and a shank portion 12, thelatter here shownas of cylindrical conformation for-the'purpose of illustration, the two being joined by a-neck portion I4 of slightly reduced diameter accordance with conventional practice. Where suchdrill blank-is to form a so-called highspeed drill, it will be appreciated that-the body I llmay be formed of such high speed steel and the shank portion .12 formed from a-lovver-grade, less ex-' pensive .and .usually softer steel, the two being joinediin the area of. the --neck I 4,- -this being-in accordance .with. conventional-practice. It will also be understoodthat the particular drill blank Tshown imFig. 1. is originally made under such conditions from two cylindrical-sections of steel which are'welded together in-the area of the neck Hand .thereafter turned to an outside diameter 'slig'htly.ilarger. than that desired in the final and extending fromsthe. free end of the main body portion '10 .to a point adjacent to butshort 1 0 of the neck l4. While the grooves [6 may be' formed in the blank many suitable mannen'they are preferably machined therein and the, machining operation preferably employed is a milling operation, such as is illustrated in Fig. 2 in 3 drill, the shank l2, as best illustrated in Fig.3, is provided with an axial bore 22 therein. which leads from its free end through the neck E4. and down into the body I 0, and a passage 24 is drilled through the metal between the bottom of each groove l6 and the bore 22, so as to communicate the bore 22 with the grooves I6 and therefor with. the oil holes which are eventually to be formed in the drill.

The next operation performed on the blanks:

beads 26 form a portion of the side walls of the corresponding groove 16 along the open sides of such grooves. In the broader aspects of the invention, they may be formed in any suitable of the rolls 34 are preferably dished or concave to such, an extent as to be complementary to the periphery of the portion of the drill bodyfollow-- "ing the trailing edge of the flute and forminga clearance therefor. In practice, the rolls 34 are mounted upon suitable arbors 35, they are prefer ably driven in synchronism with eachother, and.

. the blank is reciprocated between them while the rolls 3!] are gradually drawn toward one another. During this operation, the peripheries of the rolls 34 acting upon the lips 26 draw the lips 26 on each side of each groove l6 toward one another, more or less in the nature of a bending operation, until the tips or free edges of the lips or beads 26 are forcibly brought into contact with each other with such firmness as to effectively seal the joints between them, as brought out in Fig.5. This operation as above explained and as shown inFig. 5,

completes the formation of the oil holes 32.

manner, but it is preferred. to form them by a milling operation, and such operation is, therefore, disclosed in Fig. 4. In the particular case shown, it is accomplished by the use of a milling:

cutter 28 having peripheral cutting edges of inverted V-like conformation as shown, and in the milling operation the cutter 28 is centrally'ar-- ranged with respect to a plane including the axis:

of the blank and the center of the corresponding: groove l6. While the amount of V of the cutting edges of the milling cutter may vary so as to provide the lips or beads 26 of any desired radial dimension or depth, preferably the depth of the V is such that when the milling cutter is imbedded in the work the desired distance, the depth of the supplementary groove 30 thus cut by the milling cutter 28 and disposed centrally of the corresponding groove [6, as disclosed in the lower portion of Fig. 4, is of substantially the same depth as the clearance preferably provided back of the trailing edge of each flute, as indicated in Fig. 7, and which will hereafter be discussed in greater detail. Also, the sides of the milling cutter 28 are preferably perpendicular to its axis of rotation so that the sides of the supplementary groove 30 are straight and parallel to each other and to the central plane of the cutter 28.

' Although the flutes of the drill may now be milled or otherwise formed in the blank, I prefer, as above stated, to close the groove I 6 before such flutes are formed therein, and, accordingly, in the drawing the next step, which is illustrated in Fig. 5, comprises closing the lips 26 over the outer sides of the grooves l6 to produce the oil holes 32 desired in the finished product. While this may be accomplished in any suitable manner in accordance with the broader aspects of the present invention, it is preferably accomplished by means of apparatus such as illustrated in Fig. 5. This comprises a pair of rolls 34'of a rim width such as to be relatively closely but slidably received between the opposite side walls of the supplementary grooves 30. The peripheries 'tice.

The rolls 30, in fitting between the side walls of their corresponding supplementary grooves 30, cooperate with such side walls to hold the drill blank centrally'between them and effectively prevent any 'sidewise slippage of the blank during this operation, thus overcoming one of the difficulties experienced in carrying out the closing of the grooves inmy prior patent aboveridentified. Nevertheless, if desired, guiding rolls 33 may be disposed'at each side of the blank during the operation disclosed in Fig. 5 to insure the central relation of the blank with respect to the rolls. It will be appreciated that the rolls 33 will cooperate with the blank better if, as shown, the flutes have not yet been formed in the blank.

The next operation, in accordance with the particular sequence or steps illustrated in the drawing. is the operation of forming flutes 36 in ing edges of the flutes 36, such clearance which is illustrated in Fig. 7 at 38 is then provided in any suitable way, such, for instance, by a milling operation in accordance with conventional prac- In view of the fact that the peripheries of the rollers 34 are preferably formed complementary to the curvature of the relieved surfaces 38 and the rolls 34 in the operation illustrated in Fig. 5 are imbedded into the surface of the main body portion ID a distance equivalent to the relief 38 desired, it will be appreciated that the bottom of the grooves formed in the main body portion ID by the rolls 34 thus form a portion of the relieved surfaces 38.

The next step of operation, in accordance with the particular sequence of operation disclosed in the drawing, is "the twisting of the blank thus formed to bring the main body portion I 0 thereof and the flutes 36 therein into spiral conformation, and this maybe done in any suitable or conventional manner, with the result that the blanks will then assume the condition illustrated in Fig. 8. After the blank hasreached the condition illustrated in Fig. 8, if deemed necessary or desirable the flutes 36 maybe finish machined to bring them to the desired true helical conformation, cross-sectional configuration, and high state of finish, or the flutes may be left inthe; lag aired ,con'ditionfif such and op r- "ation is'jnot thought necessary. The drill may then'be hardened in accordance with convenftionalpractice, ground 'and sharpened to bring it to its'final condition. l

Having thus described my invention, what I claim by Letters Patent is: a.

'1. In the'manufacture ofan oil hole. twist drill from a cylindrical .blank, the steps of forming a pair of longitudinally extending grooves inan exteriorsurface of said blank, one of said grooves being .deeper and narrowervthan the other and .s'a'id other of said grooves being disposed equally on both sides thereof and shapedto form a bead f along" each side of the. first-mentioned groove, and 1 then simultaneously. operating upon said beads to displace them toward one another and into contacting and sealing engagement with respect to each other whereby to close the outer side of said first-mentioned groove. I

2. In the manufacture of an oil hole twist drill by theuse of a forming roll,.the steps offor'ming a longitudinally extending groovein the surface offa cylindrical drill blank, formingla second groove in said surface of said drilllblank centrally aligned with theQfirst-mentioned groove and disposed substantially equally on oppos'ite sides thereof, the widthofsaid second groove being approximately equal to. the thickness of saidformin-groll, and pressing said roll radially into the surfaceof said drill blank and effecting relative travel of said roll longitudinally of said blank while guided betweenhthe sides of said second groovethereby to displace the metal of said blank towards the center of said first-mentioned groove to close the open side thereof without closing the bottom portion thereof.

3. In the manufacture of an oil hole drill from a cylindrical blank by the use of a forming-roll,

.the steps of forming a longitudinally extending groove in the exterior surface of said blank, said groove having aradially outer portion of greater wi dth than the inner portion thereof and a radially outwardly. extending lip along the junction of each. side wall of the narrow portion of said groove and the bottom wall of the widened portion thereof, said widened portion being substantially the same width as the thickness ofsaid forming roll, and then pressing said forming roll radially, inwardly of saidblank in Contact with said lips while guided between the side wallsof .said wide portion of said groove, thereby displacing said lips toward the center line of the narrow. portion of said groove to close the open side of the narrow portion.

seal

,4." mite itigating; of an 011 holedrill from fa pylindrfical metal blank by the use of a pair of' jmetal displacing rollers, the steps of forming a pair. of longitudinally extending grooves in an exterior surface' of. said, blank on diametrically opposite sides thereof,.forming a pair of second igroovescin said blankveac-h centrally of the corresponding of said first-mentionedgrooves and disposedequally .oneithrlsidethereof, of less depth than'the 'firstQmentiOn'ed grooves of a width substantially corresponding with the width of said rolls, and of a bottom shape to provide a 1ip extending along each side of the firstmentioned grooves at the open sides thereof,

gripping said blank between said rolls with said rolls received in and guided between the side walls of the cooperating of said second-mentioned grooves, and effecting relative longitudinal movement of said blank between said rolls and simultaneously pressing said rolls toward each other andinto said blank to displace said lips toward and into contact with each other to close the open .side of the first-mentioned grooves without closing the bottom portions thereof.

.5.,The method of forming an oil hole in a drill body which comprises providing a cylindrical drill blank, cutting a longitudinal grooved portion in the external surface of the blank, cutting lantintermediate groove between opposite edges of the grooved portion and forming upstanding Jips or beads along opposite edges of the intermediate groove, and then deforming the lips or beads toward and into contacting relation with respect to each otherso as to substantially close trally of the first-mentioned groove and pressing it radially into the surface of said drill blank and effecting relative travel of said roll longitudinally of, said blank whereby to bend said lips toward and into contacting relationship with respect to each otherwithout closing the bottom of the first-mentioned groove.

4 STUART A. COGSDILL. 

